Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon

Definitions

• the innovation relates to a nickel based alloy.
• the aim for increasing combined cycle efficiency leads to increase of the hot gas temperatures in the larger downstream blades. But at the same time the cooling air usage should be kept low. Furthermore one wants to increase the length of the last blade to reduce the outlet Mach number. Hence creep becomes limiting.
• the designers are furthermore restricted by LCF at the blade attachment and in the disc, i.e. there is a limit to the extent to which they can solve the creep problem by making the the lower part of the airfoil thicker, and this limitation becomes more restricting with increasing alloy density. The problem is particularly difficult for single-shaft gas turbines.
• the alloys IN792 and CM247CC and CM247DS are known alloys. CC alloys are however preferable in the last stage because of the higher complexity of DS casting and the fact that the casting challenge increases with component size. CM247CC gives lower creep rates than IN792, but enters tertiary creep at lower creep levels and has a higher density. CM247CC and CM247DS have good castability, IN792 is nearly as good, whereas GTD-444 is likely to be difficult to cast.
• IN792 has a higher corrosion resistance than GTD-444 and CM247CC, hence GTD-444 and CM247CC will need corrosion coatings under conditions where IN792 does not, and the use of corrosion coatings, which are notoriously brittle, in long slender HCF prone blades should be avoided if possible.
• EP 1 054 072 A1 discloses high values of Cobalt (Co) and Tungsten (W) and low values of Aluminum (Al) and no Niobium (Nb).
• the idea is to have a new alloy which can be named as 'IN792' with +30K in 'creep strength'.
• the creep strength taking density into account, should be 30K better than for IN792 in the 973K to 1223K range while the processability like casting and heat treatment, all other mechanical properties, the corrosion resistance and the oxidation resistance should be similar or better compared to IN792.
• Molybdenum (Mo) and Tungsten (W) participate to the strength of the ⁇ matrix, wherein Aluminum (Al), Titanium (Ti), Tantalum (Ta), Niobium (Nb) and Hafnium (Hf) form ⁇ ' particles and wherein Titanium (Ti), Tantalum (Ta), Niobium (Nb) and that Hafnium (Hf) strengthen these ⁇ ' particles.
• Tungsten (W) and Tantalum (Ta) are bad actors in the sense that they increase the density.
• IN792 is similar to CM247CC in density corrected creep capability despite significantly less 'Mo+W' for strengthening of the ⁇ matrix' and a significantly lower ⁇ ' particle content, but thanks to more 'Ti+Ta+Hf' for strengthening of the ⁇ ' particles and a lower density.
• Nickel based alloy comprising, especially consisting of (in wt%):
• the levels of the matrix strengthening in these alloys elements Molybdenum (Mo) and Tungsten (W) are on at least the IN792 level.
• Tantalum (Ta) has been partly or completely replaced by Niobium (Nb) and Hafnium (Hf), and in addition Aluminum (Al) has been reduced to enable inclusion of Titanium (Ti), resulting in a significantly increased strength.
• Niobium (Nb) and Hafnium (Hf) provide strengthening per at% on about the same level as Tantalum (Ta), but because of the difference in density between Tantalum (Ta), Niobium (Nb) and Hafnium (Hf), we only need about 1wt% Niobium (Nb) to replace 2wt% Ta and 1wt% Hafnium (Hf) to replace 1.5wt% Tantalum (Ta).
• 8wt% Tantalum (Ta) can be especially replaced by 3.2wt% Niobium (Nb) and 1.1wt% Hafnium (Hf).
• Titanium (Ti) to levels at which enable a high HTW resulting in good homogenization and no residual eutectics, as this is regarded as important for good mechanical properties.
• the alloys have at least a 15K in advantage in absolute creep strength and we should also get 10K to 15K in advantage thanks to a reduced density relative to IN792. Hence we get an overall density corrected advantage of about 30K in density corrected creep capability relative to IN792.
• composition is limited by following consideration:
• Titanium Ti
• Tantalum Ti
• Niobium Nb
• Hafnium Hf

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

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Citations (4)

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• 2018
  • 2018-10-10 EP EP18199591.1A patent/EP3636784A1/fr not_active Withdrawn
• 2019
  • 2019-09-05 EP EP19774061.6A patent/EP3833793B1/fr active Active
  • 2019-09-05 WO PCT/EP2019/073672 patent/WO2020074187A1/fr unknown
  • 2019-09-05 CN CN201980066793.8A patent/CN112840054A/zh active Pending
  • 2019-09-05 US US17/281,389 patent/US11441208B2/en active Active

Patent Citations (4)

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